Nowadays, an individual identification technology using wireless communication through an electromagnetic field, a radio wave, or the like has attracted attention. In particular, as a semiconductor device which communicates data by wireless communication, an individual identification technology using an RFID (Radio Frequency Identification) tag has attracted attention. An RFID tag (hereinafter simply referred to as an RFID) is also called an IC (Integrated Circuit) tag, an IC chip, an RF tag, a wireless tag, or an electronic tag. The individual identification technology using an RFID has started to help production, management, or the like of an individual object and has been expected to be applied to personal authentication.
RFIDs are divided into two types: an active type RFID which can transmit a radio wave or an electromagnetic wave containing information on the RFID and a passive type RFID which is driven using electric power of an external radio wave or electromagnetic wave (carrier wave), depending on whether it incorporates a power supply or it is supplied with electric power externally (as for an active type RFID, see Patent Document 1, and as for a passive type RFID, see Patent Document 2). An active type RFID incorporates a power supply for driving the RFID and includes a cell as the power supply. In a passive type RFID, an electric power for driving the RFID is made by using an external radio wave or electromagnetic wave (carrier wave), and a structure where a cell is not provided is realized.
FIG. 29 is a block diagram showing a specific structure of an active type RFID. In an active type RFID 3100 of FIG. 29, a communication signal received by an antenna circuit 3101 is input to a demodulation circuit 3105 and an amplifier 3106 in a signal processing circuit 3102. Normally, the communication signal is transmitted after processing such as ASK modulation or PSL modulation is performed on a carrier of 13.56 MHz, 915 MHz, or the like. Note that FIG. 29 shows an example where 13.56 MHz is used for the communication signal. In FIG. 29, a clock signal is required as a reference in order to process a signal. Here, the carrier of 13.56 MHz is used as a clock. The carrier of 13.56 MHz is amplified by the amplifier 3106 and then supplied to a logic circuit 3107 as a clock. Further, the communication signal which has been ASK modulated or PSK modulated is demodulated by the demodulation circuit 3105. The demodulated signal is also transmitted to the logic circuit 3107 and analyzed. The signal analyzed by the logic circuit 3107 is transmitted to a memory control circuit 3108, and based on the signal, the memory control circuit 3108 controls a memory circuit 3109 and retrieves data stored in the memory circuit 3109 to transmit the data to a logic circuit 3110. The signal transmitted to the logic circuit 3110 is encoded by the logic circuit 3110, and subsequently amplified by an amplifier 3111. A modulation circuit 3112 modulates the carrier in accordance with the signal. A power supply in FIG. 29 is supplied by a cell 3103 provided outside the signal processing circuit 3102 through a power supply circuit 3104. The power supply circuit 3104 supplies an electric power to the amplifier 3106, the demodulation circuit 3105, the logic circuit 3107, the memory control circuit 3108, the memory circuit 3109, the logic circuit 3110, the amplifier 3111, the modulation circuit 3112, and the like. In this manner, the active type RFID operates.
FIG. 30 is a block diagram showing a specific structure of a passive type RFID. In a passive type RFID 3200 of FIG. 30, a communication signal received by an antenna circuit 3201 is input to a demodulation circuit 3205 and an amplifier 3206 in a signal processing circuit 3202. Normally, the communication signal is transmitted after processing such as ASK modulation or PSL modulation is performed on a carrier of 13.56 MHz, 915 MHz, or the like. FIG. 30 shows an example where 13.56 MHz is used for the communication signal. In FIG. 30, a clock signal is required as a reference in order to process a signal. Here, the carrier of 13.56 MHz is used as a clock. The carrier of 13.56 MHz is amplified by the amplifier 3206 and then supplied to a logic circuit 3207 as a clock. Further, the communication signal which has been ASK modulated or PSK modulated is demodulated by the demodulation circuit 3205. The demodulated signal is also transmitted to the logic circuit 3207 and analyzed. The signal analyzed by the logic circuit 3207 is transmitted to a memory control circuit 3208, and based on the signal, the memory control circuit 3208 controls a memory circuit 3209 and retrieves data stored in the memory circuit 3209 to transmit the data to a logic circuit 3210. The signal transmitted to the logic circuit 3210 is encoded by the logic circuit 3210, and subsequently amplified by an amplifier 3211. A modulation circuit 3212 modulates the carrier in accordance with the signal. On the other hand, the communication signal transmitted to a rectifier circuit 3203 is rectified and then input to a power supply circuit 3204. The power supply circuit 3204 supplies an electric power to the amplifier 3206, the demodulation circuit 3205, the logic circuit 3207, the memory control circuit 3208, the memory circuit 3209, the logic circuit 3210, the amplifier 3211, the modulation circuit 3212, and the like. In this manner, the passive type RFID operates.
[Patent Document 1]
Japanese Published Patent Publication No. 2005-316724
[Patent Document 2]
Japanese Translation of PCT International Application No. 2006-503376